Ionic-Liquid-Gating Induced Protonation and Superconductivity in FeSe, FeSe0.93S0.07, ZrNCl, 1T-TaS2 and Bi2Se3**Work at RUC was supported by the National Natural Science Foundation of China under Grant Nos 51872328, 11622437, 11574394, 11774423 and 11822412, the Strategic Priority Research Program of Chinese Academy of Sciences under Grant No XDB30000000, the Ministry of Science and Technology of China under Grant No 2016YFA0300504, the

Abstract

We report protonation in several compounds by an ionic-liquid-gating method, under optimized gating conditions. This leads to single superconducting phases for several compounds. Non-volatility of protons allows post-gating magnetization and transport measurements. The superconducting transition temperature Tc is enhanced to 43.5 K for FeSe0.93S0.07, and 41 K for FeSe after protonation. Superconducting transitions with Tc ∼ 15 K for ZrNCl, ∼7.2 K for 1T-TaS2, and ∼3.8 K for Bi2Se3 are induced after protonation. Electric transport in protonated FeSe0.93S0.07 confirms high-temperature superconductivity. Our 1H nuclear magnetic resonance (NMR) measurements on protonated FeSe1−xSx reveal enhanced spin-lattice relaxation rate 1/1T1 with increasing x, which is consistent with the LDA calculations that H+ is located in the interstitial sites close to the anions.